As one kind of a crash reinforcing member for a vehicle, a door impact beam (also called door guard), mounted on an inner surface of a door of a vehicle, is known. In the past, a door impact beam in which brackets (mounting brackets) are welded to both ends of a pipe-shaped body is widely used. In recent years, however, a door impact beam in which a beam body and brackets are integrally stamped (pressed) is in the mainstream. In the case of the door impact beam having the integrally formed beam body and brackets, a door impact beam having an open cross-sectional shape in which a traverse cross-section of the beam body has a hat-shape becomes widespread.
In the case of a door guard for a vehicle described in patent document 1 for example, a steel plate is stamped (pressed) and a beam body and brackets are integrally formed, a bent portion 1a (including a wall, a center flange and a curved corner) having an R-shaped cross-section is integrally formed on its body portion over its entire length, and flat flanges 1b (corresponding to outer flanges) are respectively formed on upper and lower portions of a base of the bent portion. That is, the hat-shaped cross-sectional shape including the bent portion 1a and the pair of flanges 1b is uniformly formed on the body over its entire length.
A door impact beam disclosed in patent document 2 includes a raised portion 2 (including a wall, a center flange and a curved corner) and bottoms 3 (corresponding to outer flanges) on both sides of the raised portion 2 in its width direction, and these members form a hat-shaped cross-section of a body of the door impact beam. A width of the door impact beam is the largest in its center section in its length direction, the width gradually becomes smaller from the center section toward both ends in the length direction, and the smallest width continues from a portion thereof separated from the center section by a predetermined distance to both the ends in the length direction. Sizes of the hat-shaped cross-section of various portions substantially correspond to the above-described size.